The molecular dynamics of the lipid constituents of human plasma lipoproteins, particularly high- and low-density species, will be probed employing 13C NMR spectroscopy; line widths, intensities, spin-lattice relaxation times, and nuclear Overhauser enhancements will be used as indicators of restrictions on rotational reorientation of the cholesterol ring system in these complex particles. This work will be extended to the lipids of athersclerotic plaque material obtained from human sources as well as from rabbits fed two hypercholesterolemic diets. Finally, the properties of lipoprotein particles containing bound amphotericin B, nystatin, and filipin will be probed.